Exemplary embodiments of the present invention relate generally to an antenna and a method for designing an antenna. Exemplary embodiments may be particularly adapted to operate in the VHF frequency range, more particularly from 30 to 300 MHz. Other exemplary embodiments may be adapted to operate in other frequency ranges not limited to VHF, unless otherwise specified.
VHF antennas operating over the frequency range of 30-3000 MHz are widely used for short-distance terrestrial communications such as TV broadcast, amateur radio, land mobile and marine communications, air traffic control communications, and air navigation systems. Monopole antennas are most commonly used for VHF/UHF communications. However, monopoles require a quarter wavelength height and have narrow bandwidth. The known art has discussed the performance of small monopole VHF/UHF antennas for personal radios. There are also known designs for increasing the bandwidth of monopole antennas. However, these designs still require significant antenna heights. Furthermore, the known art has also discussed relatively smaller monopoles via meandering. But these monopoles do not have wide bandwidth. Recently, the known art presented wideband monopoles for VHF-UHF operations from 20 to 2000 MHz with a height of 15.24 cm and peak gain of approximately −25 dBi at 20 MHz. However, these known designs produce monopole-type patterns with a null in the direction normal to the ground plane.
In sum, known attempts to miniaturize antenna volume has resulted in an unsatisfactory tradeoff between radiation quality Q and bandwidth. For instance, dielectric loading of TM-mode radiators (such as dipoles and monopoles) leads to bandwidth reduction. On the other hand, magnetic loading of TE-mode radiators, as is the case with loop antennas, can only achieve minimum radiation Q. In such embodiments, the energy stored within the loop antenna is mainly magnetic. As a result, by loading the loop with high permeability material, less of the stored energy is near the antenna volume, implying a lower Q.
In light of these shortcomings, there is a need for a VHF antenna design with extremely small dimensions, including a low height, diameter, and/or weight. There is also a need for an antenna design adapted to operate in a defined frequency range, most preferably 30 to 300 MHz. A further need exists for an antenna design that does not exhibit monopole type patterns. An antenna design with an extremely low height of 5.08 cm operating from 30 to 300 MHz is not known to exist. There is also a need for an antenna with reduced volume to have improved Q and bandwidth performance.
An exemplary embodiment of the present invention may satisfy one or more of these needs. One exemplary embodiment provides an antenna design comprised of a conductive plate that is connected to a ground plane. A ferrite load is positioned between the conductive plate and the ground plane. An example of the antenna design may have a low profile and weight. An exemplary embodiment may also provide improved gain, radiation pattern, radiation quality, and bandwidth performance. One example of an antenna design may be adapted to operate from 30 to 300 MHz and have a diameter of 60.96 cm or less and a height of 5.08 cm or less, although other embodiments may have other dimensions and/or be adapted to operate over other frequency ranges.
In addition to the novel features and advantages mentioned above, other benefits will be readily apparent from the following descriptions of the drawings and exemplary embodiments.